Process of refining (degasifying and deoxidizing) of copper



i (cathodes) by absorption from the gases Patented July '8, 1930 UNITED;STATES PATENT OFFICE MICHAEL GEORGE CORSON, ,OF JACKSON HEIGHTS, NEWYORK PROCESS OF REFINING (DEGASIFYING AND DEOXIDIZING) OF COPPER NoDrawing. Application filed April 26, 1927, SerialNo. 186,821.

The present day practice of refining cop-- usually being an unavoidablecomponent of such gases. While'the theoretical amount of oxygen requiredfor the oxidation of this sulfur ought not to be larger than the amountof sulfur itself, the practical amount of oxygen permitted to combinewith copper in the oxidation process runs, however, beyond 0.5% andsometimes up to 1.0% of the total weight of the metal. In other Words,an excess of oxygen amounting to 1000-2000% is considered necessary forthe complete removal of sulfur.

v This large amount of oxy en calls in its turn for a prolonged periodof poling and for a considerable consumption of wooden poles. Again, theoperation of poling has to be closel v watched, since the overpoledmaterial will contain absorbed hydrogen and the ingots cast of it willbe gassed.

I have-found that neither the excessive oxidation, nor the prolongedpoling are really necessary. I have found that the process of oxidationpertains only to copper and not to sulfur, since there is always enoughoxygen in the copper during its sojourn in the. furnace to take care ofthe sulfur by forming S0 gas. The oxidation is only a secondaryphenomenon to the blowing away of the low pressure layer of sulfurdioxide gas coveringthe surface of the molten metal. This blowing awayofisulfur dioxide destroys the equilibrium between the sulfur dioxide onthe one a hand and sulfur plus oxygen on the other, as

dissolved in copper, and as a consequence a continuous evaporation ofsulfur dioxide takes place.

k I have discovered thatthe removal of sulfur, i. e., sulfur dioxide,will take place with- Renewed November 12, 1929.

out over-oxidizing copper if the molten metal is kept under vacuum.lVith thetotal gas pressure over the molten copper maintained at say 1+5of'mercury, a rapid and prac-' tically complete removalvofsulfur'dioxide takes place and the moltenmetal can be made to containnot more than 0.10% oxygen.

My invention also includes the removalof the oxygen from the moltencopper. While poling may be retained for the elimination of the bulk ofoxygen, it cannot result in a sound metal, unless about 0.04% of oxygenare allowed to remain in the metal. This amount of oxygen produces about9% by volume of a copper-copper-monoxide eutectic and the latter causesav large number of troubles in various industrial applications ofcopper.

All other methodsof a complete deoxida' tion of copper proposed and useduntil the present, consist in the introduction of some reducing agent,which for the sake of efliclent use must be soluble in copper. The

amount of this reducing substance cannot be strictly calculated and hasto be introduced in a considerable excess. This results either in theformation of a solid solution (in case of' phosphorus, SlgllCOIl andmanganese) or of a secondary constituenta compound of copper-with the'reducingfageilt (in the case of magnesium, calcium, cerium). Inthefirst case the electric conductivity is impaired, in

the second the metal is likely to be dirty and to cause troubles in itsfuture uses. I

Other reducing agents, for instance boron suboxide and calcium carbidehave been suggested and actually used. These substances remain, however,solid at the melting point of copper and float upon the latters surface,whence their reducing action may not be efficientandreliable.

I have found that calcium carbide may form a cheap and highly efficientreducing agent provided it is present-in a liquid form. For this purposeI dissolve calcium carbide in some molten fluoride or a mixture of fluorides. Among these sodium'fluoride, calcium fluoride, aluminum-sodiumfluoride. (cryolite) represent good solvents for calcium car- Ingeneral, my process of refining copper may be presented as follows:Cathode or native copper is continuously melted in the usual type ofreverberatory furnace and amounts of the molten metal are withdrawnperiodically and placed in an auxiliary furnace of some kind, which isso arranged as to make it possible to close it reasonably airtight soenabling a strong vacuum pump to produce a vacuum with aremaining'pressure of 15.". In a few minutes the total amount of sulfuris eliminated as sulfur dioxide. Next the molten metal is covered with aroughly powdered mixture of fluorides-and calcium carbide, though it isalso possible to introduce this mixture in a liquefied form. A violentreaction startsimmediately and after a few minutes the layer of thereducing mixture becomes quiet which indicates the end of reduction(deoxid ation) the metal is immediately ready for pouring, and nocontamination of any kind results. This process of deoxidizing with theaid of a liquid layer of a mixture of fluorides and I calcium carbide isnot limited to use in conjunction with the removal of sulfur. dioxide bythe application of a vacuum. It can be as well applied to-the moltenoxidized copper resulting from the process of removing sulfur byoxidation as is usually done in the refineries. It can also be used as asupplenot, therefore, become oxidized and no film of any oxide may befound in alloys manu factured in this way.

Claims: 1; A process of purifying copper which comprises forming a bathof metal, oxidizing any sulfur present to sulfur dioxide, and thenlowering the pressure upon the surface of the bath to a pointsubstantially below atmospheric and maintaining such condition until thesulfur dioxide has been removed.

2. A process of purifying copper which comprises forming a bath ofmetal, oxidizing bide at .the temperature of the molten metal todeoxidize the same. I j

3. A process of deoxidizing copper which comprises treating theoxygen-containing metal while molten with a mixture of calcium carbideand fluorides capable of dissolving the carbide at the temperature ofthe molten metal.

4. A process of deoxidizing copper which comprises treating theoxygen-containing metal while molten with a mixture comprising calciumcarbide and sodium fluoride.

5. A process of deoxidizing copper which comprises placing a'mixture ofcalcium carbide and fluorides upon the surface of a bath of copper, thefluorides being so chosen and present in such amount as to insure thedissolution of thev calcium carbide in the fluorides under the influenceof the heat of the bath, and maintaining. the bath fluid until thecopper has become substantially deoxidized. 6. A process of deoxidizinga copper-containing bath which comprises forming a layer of moltenfluorides upon the bath, dissolving calcium carbide therein, andmaintaining the bath fluid until it has become substantially deoxidized.

7. A process of deoxidizing copper which.

comprises treating the oxygen-containing metal while molten with amixture compris ing calcium carbide and cryolite.

Signed at 8108 Polk Ave. Jackson Heights in the count-y of Queens andState of New York this twenty-third day of April A. D.

MICHAEL GEORGE CORSON.

1 any sulfur present to sulfur dioxide, then lowering the pressure uponthe surface of the bath to a point substantially below atmos pheric andmaintaining such condition until the sulfur dioxide has been removed,and then treating with a mixture of calcium carbide and fluoridescapable of dissolving the car-

